There is a long felt need in the medical community for improved methods of measuring the volume and perimeter of large wounds. As detailed in articles by Diane K. Langemer (“Comparison of 2 wound volume measurement methods,” Advances in Skin & Wound Care, July/August 2001, hereinafter, “Langemer”, hereby incorporated by reference into the present patent application in its entirety) and Rosie Pudner (“Measuring Wounds,” Journal of Community Nursing, Volume 16, Issue 09, September 2002, hereinafter, “Pudner” hereby incorporated by reference into the present patent application in its entirety), known wound volume measurement techniques include wound molds, disposable gauges such as the Kundlin wound gauge (U.S. Pat. No. 4,483,075, hereby incorporated by reference into the present patent application in its entirety), and stereo photogrammetry (SPG).
Wound molds can provide relatively accurate measurement of wound volume but are time consuming, and expose a patient suffering from the wound to discomfort and risks of infection. The Kundlin gauge provides faster measurement capability relative to a wound mold, but still exposes the wound to contact with a foreign object (the gauge), thereby resulting in an increased risk of patient discomfort and infection. Moreover, accuracy and repeatability of the Kundlin gauge is relatively poor, and measurements using it still require 15-20 minutes. Langemer.
SPG is a non-invasive method that is reportedly more accurate then the Kundlin gauge, but the method is not suitable for certain types of wounds and is also time consuming and requires training. Pudner.
Use of structured light systems, e.g., laser scanners, for wound volume measurements has been considered. However, known techniques have proven ineffective for certain types of wounds, e.g., deep tracking wounds, large circumferential wounds, or wounds with undermining at the edges, and where the patient's position is not constant. Id. The problem of applying laser scanners to measurements of live subjects is discussed in Oberg, U.S. Pat. No. 4,821,200 (hereinafter, “Oberg”) and Song, et al., U.S. Pat. No. 6,493,095 (hereinafter “Song”). Oberg describes a method of imaging and analyzing a laser line projected onto an amputee's stump. As illustrated in Oberg, FIG. 1, the method requires the subject to be immobilized in an apparatus during the measurement procedure. The apparatus described in Oberg is highly undesirable for use with a patient suffering from a large, unhealed wound. The practical problems of immobilizing a living being for the duration of a laser scanning procedure are also noted by Song, col. 1, 11. 43-44.
Fright, et al., PCT/NZ2006/000262, (hereinafter, “Fright”) describes using optical triangulation with a camera and laser for wound volume estimation. The apparatus disclosed in Fright is stationary relative to the wound under inspection and is unable to accurately image nonplanar wounds. Since most large wounds have a substantial nonplanar aspect, this is a significant deficiency.
Thus, improved methods for non-invasive measurement in three dimensions of the boundary of a wound are needed.